The 38-year-old English actress, who welcomed baby boy Bear on Dec. 7, graces the cover of the February 2014 issue of Glamour UK. The blond beauty, who looks chic in a gray wool jacket, opens up the magazine about the newest addition to her family.
"We haven't ever really had that conversation; it was always going to have my name," the Oscar winner reveals matter-of-factly. Rocknroll was born Abel Smith but had his name legally changed.
Winslet is already mom to Mia, 13, with first husband Jim Threapleton, and Joe, 10, with ex-hubby Sam Mendes. Her two older children have their father's last names.
"Mia and Joe have it as part of their name, so it would be weird if this baby didn't," she adds. "Of course we're not going to call it RocknRoll."
As for those who might be critical of Winslet's naming decision, the mother of three doesn't really care about differing opinions on the topic.
"People might judge all they like, but I'm a f--king grown-up," she explains.
Kate and Ned, a nephew of billionaire Virgin mogul Richard Branson, quietly tied the knot in December 2012 after about a year and a half of dating. In June, the couple confirmed that they were "delighted" to be expecting their first child together.
As for getting back to her pre-pregnancy body, Winslet divulges that is the last thing on her mind right now.
"Having just had a baby, I'm not going to be thinking about my arse," she says.